CLICK HERE to see which Glee star bared all from behind!!!CLICK HERE to see which Glee star bared all from behind!!!CLICK HERE to see which Glee star bared all from behind!!!CLICK HERE to see which Glee star bared all from behind!!!

Zayn previewed the duet by posting a black and white pic of himself with Swifty on his Instagram -- but hey, she is bestiez with his girlfriend Gigi Hadid, so it wouldn't be unusual that they hang out... But collab?!